Arsenic trioxide with ascorbic acid and high-dose melphalan: results of a phase II randomized trial

Arsenic trioxide (ATO) is synergistic with ascorbic acid (AA) and melphalan against myeloma both in vitro and in vivo. The aim of this randomized phase II trial was to determine the safety and efficacy of a combination of ATO, melphalan, and AA as preparative regimen in 48 patients undergoing autologous hematopoietic stem cell transplantation (ASCT) for multiple myeloma (MM). Forty-eight patients received melphalan 200 mg/m2 i.v. over 2 days and AA 1000 mg i.v. over 7 days in 3 treatment arms: no ATO (arm 1), ATO 0.15 mg/kg i.v. x 7 days (arm 2), and ATO 0.25 mg/kg i.v. x 7 days (arm 3). No dose-limiting toxicity, engraftment failure, or nonrelapse mortality (NRM) was seen in the first 100 days post-ASCT. Complete responses (CR) were seen in 12 of 48 patients (25%), with an overall response rate (ORR = CR + PR) of 85%. Median progression-free survival (PFS) was 25 months; median overall survival (OS) has not yet been reached. There was no significant difference in CR, PFS, or OS among the 3 treatment arms, and no adverse effect of ATO on melphalan pharmacokinetics. Addition of ATO + AA to high-dose melphalan is safe and well tolerated as a preparative regimen for MM.